From Patent Specification DD No. 205 039, a generic high-voltage direct-voltage source is known which can be used in high-voltage test engineering. It consists of a battery of high-voltage capacitors which are charged up via a charging circuit. The charging circuit contains an alternating-voltage supply source, a rectifying arrangement and a switching device in series with the capacitor bank. A part of the high-voltage capacitors is grounded on one side and a monitoring unit is connected in parallel with each of these high-voltage capacitors grounded on one side, which unit emits a signal after a predetermined limit value of the permissible charging voltage for the high-voltage capacitors has been exceeded. This signal then acts on a control device which prevents further charging of the capacitor bank. Each of the monitoring units has at its input a resistive voltage divider 7 the low-voltage-side resistance of which is grounded on one side and is connected in parallel with one limit-value detector in each case. The limit-value detector is effectively connected to an evaluating unit which forms the output of the monitoring unit.
In this high-voltage direct-voltage source, voltages proportional to the charging voltage at the high-voltage capacitor are tapped off at the input of the respective monitoring unit. This proportionality is maintained even in the range of the permissible limit value of the charging voltage. Thus, small voltage rises due to electric disturbances which are possible at any time in high-voltage test engineering can lead to an unnecessarily early response by the limit-value detector.